1. Technical Field
This technology pertains generally to systems and methods for characterization of viscoelastic materials, and more particularly to in-situ characterization of rheological properties of a viscoelastic material.
2. Background Discussion
Rheology, also known as the study of the flow of matter in the liquid or “soft solid” state, is generally performed via a macroscopic rheometer that cannot be used in-situ and requires samples with significantly large volumes. Furthermore, use of existing macroscoping rheometers for delicate viscoelastic samples, and specifically for biological samples, is difficult, and in some cases impossible.
In order to characterize small samples, microrheology using microspheres (e.g. magnetic beads) has been developed; however the use of such microspheres sacrifices accuracy, and results in uncertainty. Microrheology using microspheres has limited applicability, especially in the characterization of biological samples and in-situ characterization of live tissues.
In therapeutic treatment, intravitreal injection of drugs or implantation of intravitreal drug delivery systems have become a more frequent way to administer treatment in different ocular pathologies such as age related macular degeneration, macular edema, endophthalmiti, etc. Most of these therapeutic treatments directly affect viscoelastic properties of the vitreous gel and molecular structures. However, the delivery of drugs to the eyes presents many challenges, most of which are owed to the complexity of the structure of the vitreous and its unpredictable viscoelastic changes during treatment. Therefore, it is essential to systematically monitor such changes in clinical research or treatment in order to optimize the design of drug delivery devices as well as the schedule for intravitreal injection. The main challenge, however, is the fact that its structure is extremely fragile in nature. In order to measure its bulk rheological properties using conventional rheology, the eye must be dissected, and vitreous needs to be removed. This further alters its properties and makes the measurements extremely difficult.